Barn Fires: Baled hay can catch fire if stored between 30 to 40%
moisture due to heat produced by microorganisms and plant respiration.
Hay baled at safe moisture levels of 20% or less may rise to a temperature
of 130 to 140° F for a few days before gradually cooling off. If
hay temperature rises above 140° F, temperature should be monitored
every few hours. At temperatures between 150 and 160° F, it is time
to prepare to remove hot hay from the stack or secure a source of water
in case temperature continues to rise. It would be wise to call the fire
department when hay temperature exceeds 180° F. When temperature
reaches 200° F, bales may burst into flames when removed from the
stack if not wetted.

Insect Management: Spider mites do not often cause wide spread
damage to alfalfa grown for hay and damage may be associated with water
stress. Spider mites feed by inserting long needle-like mouth parts into
leaves removing plant sap causing a yellow stippling on leaves and leaves
are covered with webbing. Severe feeding causes necrosis, leaves turn
brown, become dry and drop from the plant. Infestations are usually confined
to the lower leaves so damage starts in the lower plant canopy moving
upward. Feeding damage reduces yield, quality and retards regrowth. Spider
Mite Species in Western Arizona & Southern California include: carmine
spider mite (T. cnnabarinus Boisdival); desert spider mite (T.
desortorum Banks); strawberry mite (T. turkestani Ugarov &
Nikolski); and twospotted spider mite (Tetranychus urticae Koch).
Avoid using pyrethroid insecticides for alfalfa pest control; they can
flare spider mite infestations. Minimizing crop stress through improved
irrigation; when fields are watered, infestations often clears up in a
few days. When severe infestations occur, sulfur may be used to suppress
the populations.

Weed Control: Swine cress (Coronopus didymus) was found
this year in an alfalfa field on the south Yuma Mesa. This is a winter
annual in the mustard family that is a common urban weed but can be a
problem in alfalfa as well. The more difficult to control and invasive,
coronopus squamatus, is more vigorous and invasive and is found in the
Imperial Valley but has not, to our knowledge, been found in Yuma. Both
are controlled with Pursuit while many other herbicides are weak or ineffective
on these weeds.

Issued in furtherance of Cooperative Extension work, acts
of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture,
James A. Christenson, Director Cooperative Extension, College of Agriculture
and Life Sciences, The University of Arizona.

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